The formation of sandwiches of antigen and antibody and their use in immunoassays has been in use for over fifteen years. The art has seen two distinct trends in the field. The earliest trend was toward the formation of ternary complexes, i.e., complexes of the form --Ab.sub.1 --Ag--Ab.sub.2 *, where Ab.sub.2 * carries some label. The later trend is to multiple component systems, usually quaternary, but sometimes involving five or more components. The prior art discussion maintains this distinction.